This invention relates to a filter device comprising a filter element arranged in a filter housing that is closed by a housing cover, in which a medium to be filtered is supplied to the filter element through an inlet in the filter housing, and filtered medium is discharged through an outlet in the filter housing on the filtered side of the filter element, and in which a pressure relief valve is integrated into the housing cover and is subjected to the pressure on the inlet side of the filter element. Filter devices according to the invention are particularly suitable for filtering gases vented from the crankcase of an internal combustion engine.
Filter devices for crankcase venting, also known as oil separators, are used for filtering and purifying oil-laden air from the crankcase, the separated oil being recycled back to the oil circuit, and the filtered air being introduced into the intake tract of the internal combustion engine as a rule. The inventive filter device comprises a filter element in a filter housing which is supplied with oil-laden air through an inlet, the purified air being removed through an outlet in the filter housing. For safety reasons, a pressure relief valve is integrated into the housing cover, this valve being acted upon by the pressure of the oncoming flow side, i.e., the raw side, of the filter element and being switched to an open position when a limiting pressure is exceeded in order to relieve the pressure in the filter housing.
Such filter devices usually have a cylindrical shape, and the pressure relief valve is usually positioned in a housing cover on an axial end face of the filter. The pressure relief valve is held in the housing cover and is acted upon in its closed position by a valve spring. As soon as the excess pressure in the filter housing exceeds a value at which the pressure relief valve is opened against the force of the valve spring, the oil-laden air flows out of the filter housing through the valve.
The housing cover is inserted into a housing port on the axial end face of the filter housing and is sealed by a peripheral sealing ring between the inside of the wall of the housing port and the outside of the housing cover. The housing cover is usually screwed into the housing port, a thread being provided for this purpose between the wall of housing port and the housing cover.
If the housing cover is to be removed, e.g., for maintenance purposes, there is the risk that the rotational motion for opening the housing cover might result in damage to the sealing ring, which may be stuck tightly between the two components, in particular after a residence time between the wall of the housing port and the housing cover, so that a relative rotational motion between the filter housing and the housing cover may result in high forces acting on the sealing ring in the peripheral direction, possibly damaging the sealing ring. Likewise, adhesion of the sealing ring may result in a great increase in the force which must be exerted to open the housing cover.
It is an object of the invention to provide an improved filter device, particularly one suitable for filtering crankcase vent gases from a crankcase of an internal combustion engine.
Another object of the invention is to provide a filter device which is invention is based on the problem of creating a filter device having a simple construction and including a pressure relief valve.
A further object of the invention is to provide a filter device with a pressure relief valve in a housing cover, where the valve is protected from contamination and/or damage.
An additional object of the invention is to provide a filter device with a pressure relief valve which reliably prevents damage or injury from an oncoming flow of a hot gas/oil mixture if the pressure relief valve is opened.
These and other objects are achieved in accordance with the present invention by providing a filter device comprising a filter element disposed in a filter housing having a housing port closed by a housing cover, said filter housing having an inlet for supplying a medium to be purified to an unfiltered side of the filter element and an outlet for discharging purified medium from a filtered side of the filter element, and a pressure relief valve arranged on the housing cover and subjected to a pressure on the unfiltered side of the filter element, wherein the housing cover is constructed in two parts and comprises an inside cover and an outside cover; the pressure relief valve is mounted on the inside cover, the inside cover closes the housing port, and a discharge path is formed between the inside cover and the outside cover for discharging any medium vented from the filter housing through the pressure relief valve.
Further advantageous features and refinements are described hereinafter.
The filter device according to this invention has a two-part housing cover comprising an inside cover and an outside cover, and a pressure relief valve situated in the inside cover. A discharge path is formed between the inside cover and the outside cover for discharging a medium which escapes when the pressure relief valve is opened.
In a first preferred embodiment, the inside cover and the outside cover have different functions. The inside cover is the carrier of the pressure relief valve and also serves to provide a pressure-tight seal of the housing port in the filter housing into which the inside cover is inserted. The outside cover extends over the inside cover including the pressure relief valve and thus protects the valve from contamination from the outside. The outside cover does not have any sealing function, so sealing elements are not required between the housing wall and the outside cover. It is sufficient to provide such sealing elements, in particular a sealing ring, between the inside cover and the wall. In addition to protecting against soiling, the outside cover also provides protection against mechanical damage to the pressure relief valve.
According to another preferred embodiment, the discharge path between the inside cover and the outside cover is formed by the fact that the two covers are situated with a distance between them, so that the discharge path assumes the form of a disk-shaped space between the two covers, the diameter corresponding essentially to that of the inside cover and/or the outside cover. In another alternative embodiment, however, it may also be advantageous to arrange the inside cover and the outside cover with one directly on the other and to provide discharge paths between the outlet of the pressure relief valve in the inside cover and the environment, e.g., in the form of grooves which are created in the inside cover and/or the outside cover.
The discharge path between the inside cover and the outside cover offers the additional advantage that the pulse of the fluid escaping in the discharge path when the pressure relief valve is opened is weakened, so that the fluid escaping from the filter device produces little or no pressure surge when discharged into the environment. The velocity of flow of the fluid is reduced significantly in the discharge path.
The outside cover is advantageously connected to the wall of the housing port by a securing device, whereby the securing device allows adequate flow paths for discharging the medium into the environment. These flow paths may be designed, e.g., as recesses in a mounting thread between the outside cover and the wall surrounding the housing port.
In yet another advantageous embodiment, the inside cover and the outside cover are connected by a latched connection which has the advantage that it makes it possible in principle to omit a connection between the inside cover and the wall of the housing port, and the inside cover is secured axially only by the latching device between the inside cover and the outside cover. Axial forces acting on the inside cover are transmitted via the latching device to the outside cover and are also transmitted from the outside cover to the wall of the housing port via the securing device. In this embodiment, the outside cover, in addition to its protective function, also assumes the function of axially securing the inside cover.